一、问题描述
对输入的多个文件进行合并,并剔除其中重复的内容,去重后的内容输出到一个文件中。
file1.txt中的内容:
20150101 x
20150102 y
20150103 x
20150104 y
file2.txt中的内容:
20150105 z
20150106 x
20150101 y
20150102 y
file3.txt中的内容:
20150103 x
20150104 z
20150105 y
二、MapReduce程序
编写MapReduce程序,运行环境参考我的上一篇博客Intellij Idea配置MapReduce编程环境
package com.javacore.hadoop;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import java.io.IOException;
/**
* Created by bee on 17/3/25.
*/
public class FileMerge {
public static class Map extends Mapper<Object, Text, Text, Text> {
private static Text text = new Text();
public void map(Object key, Text value, Context content) throws IOException, InterruptedException {
text = value;
content.write(text, new Text(""));
}
}
public static class Reduce extends Reducer<Text, Text, Text, Text> {
public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
context.write(key, new Text(""));
}
}
public static void main(String[] args) throws Exception {
// delete output directory
FileUtil.deleteDir("output");
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://localhost:9000");
String[] otherArgs = new String[]{"input/filemerge/f*.txt",
"output"};
if (otherArgs.length != 2) {
System.err.println("Usage:Merge and duplicate removal <in> <out>");
System.exit(2);
}
Job job = Job.getInstance();
job.setJarByClass(FileMerge.class);
job.setMapperClass(Map.class);
job.setReducerClass(Reduce.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(Text.class);
FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
三、输出
20150101 x
20150101 y
20150102 y
20150103 x
20150104 y
20150104 z
20150105 y
20150105 z
20150106 x